Upper leg stump endoprosthesis for an exoprosthetic provision

ABSTRACT

The invention relates to an upper leg stump endoprosthesis for an exoprosthetic provision of a patient having undergone above-knee amputation. According to the invention, the upper leg stump can be inserted into a shank to which a below-knee prosthesis with a foot part is fitted. The inventive prosthesis includes a proximal shaft which is implantable in a truncated femur; an open-mesh, three-dimensional netting structure covering at least partially the proximal shaft; an adapter connected to a distal end of the proximal shaft; and a substitute condyle element, constituting a replica of a natural condyle of a knee joint, and linked to said shaft by said adapter.

FIELD OF THE INVENTION

This invention relates to a femoral-stump endoprosthesis for theadaptation of exoprosthetic provisions for a patient with an amputatedfemur.

DESCRIPTION OF THE RELATED ART

It is common practice to fit the femoral stump of the object patientwith a funnel or shank consisting for instance of a tough, elasticplastic to which the remainder of the prosthesis such as artificial kneejoint, lower leg and foot are attached.

A major problem is the exposure of the femoral stump to pressuresbearing on it via the tissue. There is, after all, muscular tissuebetween the truncated femur and the exterior of the femoral stump which,when moved, is constantly subjected to considerable pressure withoutsuch contact contributing to a sensation of natural walking.

The publications DE-A-43 38 746 and DE-C-31 25 268 describefemoral-stump implants aimed at solving the aforementioned problem byinserting in the femoral stump a shaft section which is permanentlyfastened in the bone canal. At its distal end the implant is providedwith an enlarged, mushroom-shaped head which is thought to distributethe load over a larger area. Compared to traditional adaptation optionsthis type of adaptation would hold the promise of improved wearingcomfort, even though the sensation felt by the patient concerned haspractically nothing in common with the natural sensory perception beforethe amputation.

SUMMARY OF THE INVENTION

Against that background it is the objective of this invention to improveon the femoral-stump endoprosthesis first above mentioned in a way as tosignificantly enhance the sensory perception of the patient to wherewalking feels more natural.

The present invention provides a femoral-stump endoprosthesis for anexoprosthetic provision for a patient with an amputated femur. Theendoprosthesis can be inserted in a shank to which connects thereplicated knee-joint, lower-leg and foot prosthesis. The endoprosthesisincludes a proximal shaft which is implantable in a truncated femur; anopen-mesh, three-dimensional netting structure covering at leastpartially said proximal shaft; an adapter connected to a distal end ofsaid proximal shaft; and a substitute condyle element, constituting areplica of a natural condyle of a knee joint, and linked to said shaftby said adapter.

Specifically, the endoprosthesis incorporates a proximal shaft which isimplantable in a femoral stump, which is at least partially covered withtextured three-dimensional netting and which is provided at its distalend with a cone-shaped adapter serving to link a metallic substitutecondyle, replicating the natural condyles of a knee joint, with the saidshaft.

The three-dimensional open-mesh netting, also referred to asinterconnective netting, permits natural bone tissue to grow into,through, behind and around it during the adaptive healing processwhereby, after a relatively brief period—at least with regard to thesubstrate flow—the implanted shaft section will be integrated in thefemur, ensuring extremely sturdy secondary fixation. Growing bone tissueinto an open-mesh, three-dimensional netting is a process essentiallyknown in the field of pure endoprosthetics. In that context, referenceis made for instance to the German patent DE-PS 41 06 971.

The cone-shaped adapter provided at the distal end permits theattachment of a solid element, i.e. the substitute condyle. The adaptercone is composed of a conical collet with a conical clamping tenon,where the collet may be made a part of the shaft section while the tenonis integrated into the substitute condyle.

The substitute condyle distributes the pressure load over a larger area,while especially the replication of the natural condyles results in amore natural feeling, known as osteoperception, on the part of thepatient.

The effect is further enhanced by the fact that the lining of the shankwhich is fitted over the femoral stump simulates the shape of thenatural femoral sliding parts within a natural knee joint. Replicatingin the substitute condyle the shape of natural condyles provides theclamping for the simulated sliding parts, substantially improving thebonding of the femoral stump of the patient while walking.

In an advantageous form of implementation, the substitute condyleconsists of a basic metal body coated with an impact-absorbing plasticlayer. This impact-absorbing layer prevents shocks from reaching theremaining femoral stump unattenuated. It can also help improveosteoperception, considering that in the case of a healthy person aswell, shocks to which the knee and ankle joints are exposed are nottransmitted to the femur unattenuated.

To be effective, the impact-absorbing layer is preferably 3 to 10 mmthick.

In a particularly preferred embodiment, the impact-absorbing layerconsists of silicone, a material which has inherently resilientbuffering properties and is extremely well suited to the applicationwithin the scope of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings wherein like elements are numbered alikein the several FIGURES:

FIG. 1 is schematic view of a femoral stump with a femoral stumpendoprosthesis implanted in a truncated femur.

The following will explain this invention in more detail with the aid ofone drawing.

The drawing is a schematic illustration of a femoral stump 1, with afemoral-stump endoprosthesis implanted in the truncated femur 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a schematic illustration of a femoral stump 1, with afemoral-stump endoprosthesis implanted in the truncated femur 5.

The proximal section of an intramedullar shaft 4 is implanted in thetruncated femur 5. The surface of the shaft section 4 is covered with anopen-mesh, three-dimensional netting 6 through which bone tissue cangrow so that after a certain adaptive healing period, with respect tothe substrate flow, the implanted section of the shaft 4 will havebecome a more or less integral part of the natural bone.

At its distal end, the shaft 4 connects to a cone-shaped adapter 7. Byway of this cone-shaped adapter 7 the distal end of the shaft 4 islinked to the substitute condyle 11 (sic).

The substitute condyle element 8 is configured in such fashion that itreplicates the shape of natural condyles 11 in a knee joint.

In the design example illustrated, the substitute condyle element 8 iscoated with an impact-attenuating silicone layer 10.

The entire femoral-stump endoprosthesis is thus positioned within thefemur. There is no gap anywhere in the area of the femoral stump.

The femoral stump 1 is encased in a femoral shank 2 to which theassembly 3 of artificial knee, lower leg and foot is attached.

The counterpart to the condyle element 8 with its replica of a naturalcondyle 11 is a correspondingly matched section in the interior of theshank 2 which simulates the natural sliding parts of a knee joint.

The femoral shank 2 in this case consists of pressure padding 14laterally and medially fitted on the femoral stump and firmly lockedonto the femoral stump by means of a clasp 12 and a tiltable hinge 13.

The knee-joint function per se is provided by an artificial knee joint15 for instance as described in EP-C-0 358 056.

What is claimed is:
 1. Femoral-stump endoprosthesis for adaptation of anexoprosthetic provision for a patient with an amputated femur, whereby afemoral stump is enclosable in a shank to which connects a replicatedkneejoint, lower-leg and foot prosthesis, said endoprosthesiscomprising: a proximal shaft which is implantable in a truncated femur;an open-mesh, three-dimensional netting structure covering at leastpartially said proximal shaft; an adapter connected to a distal end ofsaid proximal shaft; and a substitute condyle element, comprising areplica of a natural condyle of a knee joint, and linked to said shaftby said adapter.
 2. Femoral-stump endoprosthesis as in claim 1, whereinsaid substitute condyle element comprises a basic metal body. 3.Femoral-stump endoprosthesis as in claim 2, wherein said basic metalbody is coated with an impact-attenuating plastic layer. 4.Femoral-stump endoprosthesis as in claim 3, wherein saidimpact-attenuating layer is 3 to 10 mm thick.
 5. Femoral-stumpendoprosthesis as in claim 4 wherein said impact attenuating layercomprises silicon.
 6. Femoral-stump endoprosthesis as in claim 3,wherein said impact attenuating layer comprises silicon. 7.Femoral-stump endoprosthesis as in claim 1, wherein said adapter is of acone shape.